COSRX The Vitamin C 23 serum 20ml

Product Overview

COSRX The Vitamin C 23 Serum is a high-strength serum combining 23% pure L‑ascorbic acid with antioxidant-rich oils, hyaluronic acid, and niacinamide to fade hyperpigmentation, brighten dull skin, and improve firmness and elasticity. It’s formulated in a bi‑phase design (oil + water layers) to enhance stability and texture. 

🧪 Key Ingredients & Benefits

• 23% L‑Ascorbic Acid: A potent antioxidant that aids in brightening, collagen stimulation, and reducing fine lines. 

• Super Vitamin E (Tocotrienols): Enhances antioxidant power, supports collagen synthesis, and boosts skin protection. 

• Hyaluronic Acid / Sodium Hyaluronate: Deep hydration to plump skin and maintain moisture balance. 

• Allantoin, Panthenol, Caffeine, Niacinamide, Licorice Root Extract, Glutathione, Adenosine: Soothe irritation, calm redness, improve tone, and deliver antioxidant support. 

🧴 Texture & Application

This serum features a two-layer system: a clear pure vitamin C phase and an oil-rich top layer. Shake gently before use to blend these. It has a yellowish tint from the ascorbic acid and oils. Users report a smooth absorbency, though it can feel slightly sticky—moisturizer helps if needed. 

🧭 How to Use

• Temperature-sensitive product—store upright in the fridge at 3–10 °C. Use within 2 months of opening to prevent oxidation. 

• After cleansing (during serum step), apply 2–3 drops, gently rubbing inward to outward. Pat until absorbed. Use morning or evening with sunscreen SPF 30+ when used daytime. 

✅ Ideal For

• Experienced vitamin C users seeking powerful brightening and anti-aging effects. Not generally recommended for beginners or very sensitive skin due to its high concentration. 

• Especially beneficial for those tackling dark spots, dullness, uneven tone, or aging concerns. 

🌟 Efficacy — Clinical & Community Feedback

• A clinical study on 20 subjects showed ~32% improvement in overall radiance and complexion evenness, 16–38% gains in elasticity, pigmentation reduction, and pore refinement over 4 weeks. 

• ChatGPT cited reviewers like GQ or Glamour praised it as a top-tier budget vitamin C serum, especially for experienced users. Community feedback from Reddit:

• “I swear … just a week … such a visible difference … bright and healthy.” 
  “It’s quite good! … helped fade darkspot … funny smell though.” 
  However others noted irritation or breakouts when started too quickly or used daily without initial patch tests:
  “23 % is too strong … My forehead started getting irritated bumps.” 

⚠️ Potential Drawbacks & Safety Tips

• Oxidation risk: Vitamin C oxidizes quickly. Discard if it turns dark orange or brown—even though some users report yellow tints may be normal. Keep it refrigerated and use within 2 months of opening.

• Scent: Some users describe a strong, burnt or “hotdog-like” odor—likely from gardenia-derived ferulic compounds and vitamin C. It usually fades quickly.

• May sting or irritate sensitive skin, especially at high concentration. Start with 2–3 times weekly, avoid other actives initially, and always patch test.

📋 Summary Table